If you have ever typed “what does anxiety feel like” into a search bar late at night, you were probably not asking about worry. For many people, anxiety is above all a physical experience. The heart pounds or skips, the chest feels too tight to take a full breath, the stomach churns and the hands tingle. Sometimes there is a sudden, overwhelming sense that something terrible is about to happen. The anxious thoughts often come afterwards, as the mind tries to explain what the body is doing.

In my work as a clinical psychologist, two experiences come up more than any others. The first is the feeling of not being able to breathe. The second is a sense of impending doom: a certainty, arriving out of nowhere, that you are about to collapse, lose control or die. Both are among the most frightening things a person can feel, and both are among the most misunderstood. When I explain where they come from, and how they fit into the body’s older survival responses of fight, flight, freeze and flop, I often see something shift. The sensations do not disappear, but they start to make sense, and something that makes sense is far less frightening than something that does not.

What does anxiety feel like in the body?

Consider Martin, a structural engineer in his late thirties. He would not describe himself as an anxious person. He is methodical, calm under pressure at work, and the colleague others ring when something goes wrong. Yet over a few months he has noticed his heart racing on the morning train, a tight band across his chest in meetings, and a stomach that seems permanently unsettled. Twice he has had to leave a room because he was suddenly sure he was about to faint. He has seen his GP, had blood tests and an ECG, and been told everything looks normal. That reassures him for about a day.

What Martin is experiencing is the body’s threat response, a set of changes designed for a world in which danger was usually physical and immediate. When the brain detects a possible threat, it does not wait for careful analysis. It prepares the body to act, quickly and broadly. The heart speeds up and beats harder to send blood to the large muscles, breathing quickens to take in more oxygen, and muscles tense, ready to brace or move. Almost every system in the body is adjusted in some way, which is why anxiety can produce such a wide and sometimes baffling range of sensations.

None of this was designed for an overflowing inbox, a difficult conversation with a partner or a vague sense that something at work is about to go wrong. But the system responds to perceived threat, not to whether the threat is the kind it evolved for, and so it fires in much the same way. Research on interoception, our ability to sense what is happening inside the body, suggests that anxiety is closely bound up with how we notice and interpret these internal signals.1 The findings are not entirely consistent, and it is not simply that anxious people are more sensitive to their own heartbeat. But it does seem that once a sensation has been tagged as potentially dangerous, it becomes much harder to ignore.

Which anxiety symptoms do people not recognise?

A racing heart and shaky hands are widely understood as signs of anxiety. Many of the other changes are not, and these are often the ones that send people to their GP convinced something else is wrong. The gut is a good example. Because digestion is put on hold when the body prepares for danger, and because the gut and the brain are in constant communication, anxiety frequently shows up as nausea, loss of appetite, a churning or hollow stomach, or a sudden need for the toilet. For some people the stomach is the first and most reliable sign that they are under strain, long before they would describe themselves as anxious.

Muscle tension is another. The body braces against threat, and for many people that bracing settles in the jaw, neck and shoulders. A person may wake with an aching jaw or a headache, notice they have been clenching their teeth at their desk, or find their shoulders creeping up towards their ears by the end of the day. Because this tension builds slowly and quietly, it is rarely connected with anxiety at all. It simply feels like a sore jaw or a stiff neck that will not go away.

Changes in vision can be particularly unsettling. During the threat response the pupils widen to let in more light, which can make bright lights feel harsh and the edges of vision seem slightly blurred. Attention also narrows towards whatever seems threatening, which some people experience as a kind of tunnel vision. Combined with the light-headedness that fast breathing can bring, these changes can feel alarming, and they understandably lead people to worry about their eyes or their brain.

Perhaps the least recognised of all is derealisation: the sense that the world has become flat, distant or dreamlike, or that you are watching your life from slightly outside it. People often find this harder to put into words than any physical symptom, and many are frightened that it means they are losing their mind. It is in fact a well-documented feature of intense anxiety, and it seems to reflect the brain turning down the volume on experience when arousal becomes overwhelming. It is unpleasant, but it is not a sign of madness, and it tends to fade as anxiety settles.

Why does anxiety make it feel like you can’t breathe?

The feeling of not getting enough air is one of the most distressing parts of anxiety, and it is worth understanding in some detail because the explanation is counterintuitive. In many cases, a person who feels they cannot breathe during anxiety is actually breathing more than they need to, not less. When the threat response kicks in, breathing becomes faster and shifts higher into the chest. That suits a body about to sprint. When you are sitting still at a desk, though, you breathe out carbon dioxide faster than your body is producing it, and the level in your blood falls.

Lower carbon dioxide has noticeable effects. It can cause light-headedness, tingling in the fingers or around the mouth, a slightly unreal feeling and, crucially, a sense of air hunger, as if each breath does not quite fill you up. At the same time, the muscles around the ribs tighten along with everything else, which makes the chest feel restricted. The natural response is to gulp at the air or take big sighing breaths, which tends to lower carbon dioxide further and intensify the very feeling it was meant to fix. It is a loop the body walks into with the best of intentions.

This is part of why the well-meant advice to “take a deep breath” can sometimes make things worse. The problem is rarely a shortage of air. It is a breathing pattern built for running, used in a body that is standing still. Many people find it a relief simply to know this, because it replaces the frightening thought that they are suffocating with a more accurate one: that their breathing has briefly got ahead of them.

Where does the sense of impending doom come from?

If breathlessness is the most physically frightening part of anxiety, a sense of impending doom is often the most psychologically overwhelming. People describe it in remarkably similar ways: a sudden, total conviction that something catastrophic is about to happen, often without any clear idea of what. It may arrive as certainty that they are dying, going mad or about to lose control in public. It is a well-recognised part of intense anxiety, and it is not a sign of weakness or of being dramatic. It is, in a sense, the threat response speaking in its purest form.

The brain’s alarm system is designed to make us feel danger before we can name it. That ordering makes evolutionary sense: an ancestor who waited until they had identified the rustle in the grass would not have lasted long. So the feeling of threat arrives first, and the mind then searches for an explanation. When there is no obvious external danger, the most available explanation is often the body itself. The racing heart must be a heart attack, the breathlessness must mean suffocation, and the strange, detached feeling must mean losing one’s mind.

This creates a cycle that many people will recognise. A bodily sensation is read as a sign that something catastrophic is happening. That reading increases fear, the fear produces more sensations, and those sensations seem to confirm the catastrophe. It also explains why the doom feels so convincing. It is not a thought that one considers and weighs up, but a feeling that arrives with the full authority of the body behind it.

Fight, flight, freeze or flop: why doesn’t anxiety always feel the same?

Most people have heard of fight or flight, but it is only part of the picture. Researchers who study defensive responses describe something closer to a cascade: a series of hard-wired reactions that unfold depending on how threatening, and how escapable, a situation seems.2 Fight and flight are the active responses. They produce the familiar restless, energised kind of anxiety, with irritability, pacing, an urge to get out of the room, and a jaw clenched so hard it aches by evening.

Freeze is fight or flight with the brakes on. The body is highly aroused and ready to move but held still, much as an animal goes motionless when a predator may not yet have noticed it. People often describe this as their mind going blank in a meeting, being unable to find words, or feeling rooted to the spot while their heart pounds underneath. Many people who freeze in this way later criticise themselves for not having said or done something, without realising that the response was never under conscious control.

Flop is the least well known and, for those who experience it, often the most confusing. When a threat feels overwhelming and inescapable, the body can shift in the opposite direction, slowing the heart, lowering blood pressure and reducing muscle tone. People may feel heavy, faint, numb or far away, and some do faint. This end of the cascade is thought to be linked to the experiences of unreality and detachment that frighten people so much: the sense of watching life from behind glass, or of the world looking flat and strange. In everyday anxiety, people usually touch only the edges of this state; it is most strongly associated with overwhelming and traumatic experiences.

Understanding this cascade does something important. It explains why two people with the same underlying difficulty can describe completely different experiences, one restless and wired, the other blank or detached. It also removes some of the shame. People who freeze or shut down often assume something must be wrong with them, when in fact their nervous system has done exactly what nervous systems have evolved to do.

How can you tell anxiety from a physical health problem?

This is one of the most important questions people ask, and the honest answer is that, at least at first, you often cannot tell on your own. Anxiety and physical illness can produce very similar sensations, and the overlap is greatest with the symptoms that frighten people most. Chest pain, a pounding heart, breathlessness and a sense of doom are all common in intense anxiety, but they are also signs of a cardiac emergency, which is why so many people ask whether anxiety can feel like a heart attack. It can. One review estimated that around a quarter of people who see a doctor about chest pain have an underlying anxiety disorder, and noted that this often goes unrecognised, leading to repeated visits and considerable distress.3

That overlap cuts both ways, and it matters. It is never sensible to assume that a symptom is anxiety, particularly the first time it happens, if it is severe, or if it comes with other warning signs. New or unexplained physical symptoms deserve proper medical assessment, and a good clinician will want to consider physical causes before settling on anxiety as the explanation. Being sent for tests is not a sign that anyone thinks you are imagining things; it is simply good care.

Once physical causes have been looked at, the pattern over time is often the most telling clue. Anxiety-related symptoms tend to rise and fall with stress, to cluster around particular situations or times of day, and to ease when attention is absorbed in something else. They also tend to respond to reassurance only briefly, which is part of why repeated checking can keep the cycle going. None of these features is proof, and some physical conditions behave in similar ways, so this is something to work out with a doctor rather than alone at home. If you have chest pain or severe difficulty breathing, especially for the first time, call 999; if you are struggling emotionally and need to talk to someone now, NHS 111 and the Samaritans (116 123) are available at any hour.

When is it worth talking to someone?

Some people reading this will recognise themselves in Martin. He did not experience anything he would call worry. He experienced a stomach, a chest and a heart, and assumed for a long time that the problem must be physical because that was where he felt it. This is surprisingly common among people who are used to being capable and in control, and who may have had little practice in noticing their emotional state until it announces itself through the body. It is entirely possible to be anxious without feeling worried, and for the first sign of strain to be physical rather than mental.

It is worth talking to someone when anxiety has begun to shape your life rather than simply visiting it. That might mean avoiding meetings, journeys or situations because of how your body might react, returning again and again to the GP or to internet searches for reassurance that never quite lasts, or noticing that the sensations are taking up more and more of your attention. It might simply mean that you have been told your tests are normal, felt relieved, and found that nothing has actually changed. None of this requires being in crisis. These are signs that the alarm has become a little too easily set off, and that understanding why may be worthwhile.

Psychological approaches such as cognitive behavioural therapy help people notice the cycle between sensation, interpretation and fear, and discover what actually happens when they respond to their sensations differently. Research suggests these approaches are effective for anxiety, although, as with any treatment, they do not help everyone equally.4 In my experience, what tends to shift first is not the sensations themselves but the relationship to them. A racing heart becomes something unpleasant rather than something catastrophic, and that change in meaning often allows the body to settle more quickly.

Anxiety, then, is not only a state of mind. It is one of the oldest things the body knows how to do, a system built to keep us alive that sometimes fires in situations it was never designed for. Its sensations are real, often intense and, at their worst, genuinely frightening. But they are not random, and they are rarely the catastrophe they announce themselves to be.

There is something steadying in understanding that. Many people find that the hardest part of anxiety is not the racing heart or the tight chest but the sense of being at the mercy of something they do not understand. Making sense of what the body is doing, and why, does not require being in crisis; it can be a quiet and curious piece of self-understanding. Sometimes the most useful question is not how to make the alarm stop, but what it has been trying to tell us.